Michal Suchánek <msucha...@suse.de> writes:
> On Wed, Mar 20, 2024 at 11:41:32PM +1100, Michael Ellerman wrote:
>> Michal Suchánek <msucha...@suse.de> writes:
>> > On Mon, Mar 18, 2024 at 06:08:55PM +0100, Michal Suchánek wrote:
>> >> On Mon, Mar 18, 2024 at 10:50:49PM +1100, Michael Ellerman wrote:
>> >> > Michael Ellerman <m...@ellerman.id.au> writes:
>> >> > > Michal Suchánek <msucha...@suse.de> writes:
>> >> > >> Hello,
>> >> > >>
>> >> > >> I cannot load the wireguard module.
>> >> > >>
>> >> > >> Loading the module provides no diagnostic other than 'No such
>> >> > >> device'.
>> >> > >>
>> >> > >> Please provide maningful diagnostics for loading software-only
>> >> > >> driver,
>> >> > >> clearly there is no particular device needed.
>> >> > >
>> >> > > Presumably it's just bubbling up an -ENODEV from somewhere.
>> >> > >
>> >> > > Can you get a trace of it?
>> >> > >
>> >> > > Something like:
>> >> > >
>> >> > > # trace-cmd record -p function_graph -F modprobe wireguard
>> >
>> > Attached.
>>
>> Sorry :/, you need to also trace children of modprobe, with -c.
>>
>> But, I was able to reproduce the same issue here.
>>
>> On a P9, a kernel with CONFIG_CRYPTO_CHACHA20_P10=n everything works:
>>
>> $ modprobe -v wireguard
>> insmod /lib/modules/6.8.0/kernel/net/ipv4/udp_tunnel.ko
>> insmod /lib/modules/6.8.0/kernel/net/ipv6/ip6_udp_tunnel.ko
>> insmod /lib/modules/6.8.0/kernel/lib/crypto/libchacha.ko
>> insmod /lib/modules/6.8.0/kernel/lib/crypto/libchacha20poly1305.ko
>> insmod /lib/modules/6.8.0/kernel/drivers/net/wireguard/wireguard.ko
>> [ 19.180564][ T692] wireguard: allowedips self-tests: pass
>> [ 19.185080][ T692] wireguard: nonce counter self-tests: pass
>> [ 19.310438][ T692] wireguard: ratelimiter self-tests: pass
>> [ 19.310639][ T692] wireguard: WireGuard 1.0.0 loaded. See
>> www.wireguard.com for information.
>> [ 19.310746][ T692] wireguard: Copyright (C) 2015-2019 Jason A.
>> Donenfeld <ja...@zx2c4.com>. All Rights Reserved.
>>
>>
>> If I build CONFIG_CRYPTO_CHACHA20_P10 as a module then it breaks:
>>
>> $ modprobe -v wireguard
>> insmod /lib/modules/6.8.0/kernel/net/ipv4/udp_tunnel.ko
>> insmod /lib/modules/6.8.0/kernel/net/ipv6/ip6_udp_tunnel.ko
>> insmod /lib/modules/6.8.0/kernel/lib/crypto/libchacha.ko
>> insmod /lib/modules/6.8.0/kernel/arch/powerpc/crypto/chacha-p10-crypto.ko
>> modprobe: ERROR: could not insert 'wireguard': No such device
>>
>>
>> The ENODEV is coming from module_cpu_feature_match(), which blocks the
>> driver from loading on non-p10.
>>
>> Looking at other arches (arm64 at least) it seems like the driver should
>> instead be loading but disabling the p10 path. Which then allows
>> chacha_crypt_arch() to exist, and it has a fallback to use
>> chacha_crypt_generic().
>>
>> I don't see how module_cpu_feature_match() can co-exist with the driver
>> also providing a fallback. Hopefully someone who knows crypto better
>> than me can explain it.
>
> Maybe it doesn't. ppc64le is the only platform that needs the fallback,
> on other platforms that have hardware-specific chacha implementation it
> seems to be using pretty common feature so the fallback is rarely if
> ever needed in practice.
Yeah you are probably right.
The arm64 NEON code was changed by Ard to behave like a library in
b3aad5bad26a ("crypto: arm64/chacha - expose arm64 ChaCha routine as
library function").
Which included this change:
@@ -179,14 +207,17 @@ static struct skcipher_alg algs[] = {
static int __init chacha_simd_mod_init(void)
{
if (!cpu_have_named_feature(ASIMD))
- return -ENODEV;
+ return 0;
+
+ static_branch_enable(&have_neon);
return crypto_register_skciphers(algs, ARRAY_SIZE(algs));
}
It didn't use module_cpu_feature_match(), but the above is basically the
same pattern.
I don't actually see the point of using module_cpu_feature_match() for
this code.
There's no point loading it unless someone wants to use chacha, and that
should be handled by MODULE_ALIAS_CRYPTO("chacha20") etc.
cheers
